Hydrogen Chloride Gas Research Articles

A numerical study on effective arrangement of fan-filter units in a semiconductor cleanroom: Control of hazardous gas leakage from a process instrument

Contamination control in cleanrooms is essential for maintaining high productivity across various industries. In semiconductor manufacturing environments, hazardous gas leaks from instruments can pose serious health risks to operators, especially during the preventive maintenance. In this study, the numerical simulations were performed to evaluate and optimize the fan filter unit (FFU) arrangement in a cleanroom, aiming to effectively manage hazardous hydrogen chloride (HCl) gas leakage during semiconductor instrument maintenance. To reflect the actual situation, the study incorporates leakage conditions from a reference, considering various thermal factors. The simulation results indicate that the FFU arrangement and coverage rate, which influence internal airflow under a fixed air change rate (ACH), are critical for hazardous leakage control during preventive maintenance. A quantitative and comprehensive analysis of the accumulation of leaked gas on the operator and instrument surfaces showed that the analysis score proposed in this research on the horizontal FFU array with 30% coverage was 0.44, which is minimum among different cases, indicating the best performance on controlling dispersion behaviour of the hazardous gas in the cleanroom during the preventive maintenance.

Interband cascade laser absorption sensor for sensitive measurement of hydrogen chloride in smoke-laden gases using wavelength modulation spectroscopy

A tunable interband cascade laser sensor, based on wavelength modulation absorption spectroscopy near 3.73 µm, was developed to measure hydrogen chloride gas concentration in smoke-laden environments associated with the overhaul stages of firefighting. Wavelength selection near 2678cm−1 targets the P(0,9) transition within the fundamental vibrational band of HCl, chosen for its absorption strength and isolation from CO2, H2O, and CH4, as well as proximity to absorption features of other toxicant gases of interest in firefighting applications. Both scanned-wavelength direct absorption with a Voigt lineshape-fitting routine and a wavelength modulation spectroscopy absorption method are employed to recover species concentration. The laser sensor is paired with a compact commercial off-the-shelf 1 m multipass optical gas cell modified to use polished Alloy 20 steel mirrors for increased corrosion resistance against humid and acidic gases, and it is tested by sampling effluent gases from pyrolyzing and burning solid samples of polyvinyl chloride under a radiant heating apparatus in a laboratory fume hood. The wavelength modulation spectroscopy method is demonstrated to enable measurement at the near-ppm-level within a compact form-factor and to provide insights into the thermochemical pyrolysis processes that lead to the formation of hydrogen chloride when polyvinyl chloride is exposed to radiant heating.

Fluorescence switching of triarylamine-based polyamides with pendant pyrene units and its application in electrochromic smart displays

The pyrene group was directly connected to the triarylamine (TAA) unit through a benzene bridge via the Suzuki reaction to successfully prepare the diamine monomer. A series of new polyamides (PAs) based on TAA units were prepared by polycondensation. The PAs exhibited good solution processability and high thermal stability with the char yield in excess of 53 % at 800 °C in air atmosphere. In solvents with different polarities, these PAs showed solvatochromic effect and large stokes shift. Strongly photoluminescent PAs have a sensitive stimulus response to explosive and hazardous gas, and its fluorescence is easily turned off by the addition of trinitrophenol (TNP) and hydrogen chloride (HCl). And achieve fluorescence switching between exposure to HCl and ammonia (NH3) gas. The PAs exhibited a reversible color response in the electrochemical oxidation process, with no significant degradation in current and transmittance after 200 cycles. The sandwich structure multicolor electrochromic device can achieve electrochromic performance applied by different voltages.

Development of a ReaxFF Reactive Force Field for Pt/Cl Systems with Application to Platinum Metal Etching with Chlorine and Hydrogen Chloride Gases.

In this study, we present the development of a ReaxFF Pt/Cl/H reactive force field designed to elucidate the etching process by Cl for Pt surfaces. The ReaxFF force field parameters were optimized based on a quantum mechanical training set, which included adsorption energies of Cl and dissociation of HCl on Pt(100) and Pt(111) surfaces, energy/volume relations of PtCl2 crystals, and Cl diffusion on Pt(100) and Pt(111) surfaces. The predictive capability of the force field was further established through molecular dynamics simulations, which investigated the interactions of Cl2 and HCl molecules with the (100) and (111) surfaces of c-Pt crystalline solid slabs. A comparative analysis revealed that the Pt (100) surface exhibited higher susceptibility to chlorination and etching, leading to a more dominant removal of surface Pt atoms, whereas the Pt (111) surface showed greater resistance to these processes. This resistance impeded the access of Cl atoms to the Pt surface, resulting in a slower formation of PtxCly molecules. The etching ratios between HCl and Cl2 were compared with experimental results, yielding satisfactory agreement. This indicates that the developed ReaxFF protocol serves as a valuable tool for studying atomistic-scale details of the etching process in platinum metal systems.

The removal mechanisms of HF and HCl gases using Mg-Al adsorbent prepared by sol-gel synthesis method

In this study, a series of Mg-Al mixed oxide adsorbents have been introduced to simultaneously remove hydrogen chloride (HCl) and hydrofluoric acid (HF) in low-temperature environment (100 °C). These adsorbents prepared by the sol-gel method, the effects of Mg loading amount and calcination temperature for adsorbents on their performance were investigated. The optimal adsorbent (modified by 20 wt% Mg and calcined at 500 °C, referred to as Mg20Al80OX-500) exhibited the highest adsorption capacity among all the adsorbents tested. The role of MgO loaded on Mg-Al mixed oxide adsorbent was investigated using various analytical methods, including Brunauer-Emmet-Teller (BET), X-ray diffractometer (XRD), scanning electron microscopy (SEM-EDS), thermogravimetric analysis (TG-DTG), temperature programmed desorption of CO2 (CO2-TPD), X-ray photoelectron spectroscopy (XPS)， in-situ infrared (in-situ IR) and transmission electron microscopy (TEM). These results indicated that MgO and lattice oxygen (Oα) played a crucial role in promoting the adsorption activity of the adsorbents. Mg were highly dispersed, and moderate levels of Mg content and calcination temperature could enhance the performance of adsorbents according to XRD, SEM-EDS and TG-DTG results. BET analysis showed that the modification of Mg did not change the pore type of the γ-Al2O3 largely. CO2-TPD results revealed that the calcination temperature significantly affected the number and strength of the basic sites on the surface of the adsorbent. In addition, XPS, in-situ IR and TEM analysis demonstrated that the consumption of MgO and Oα as well as the accumulation of reaction products on the surface and within the pores of the adsorbent, and they were the main reasons the deactivation. And MgF2 (MgCl2) and H2O were the main products after the inactivation of adsorbent.

Hydrogen Chloride and Sulfur Dioxide Gas Evolutions from the Reaction between Mg Sulfate and NaCl: Implications for the Sample Analysis at the Mars Instrument in Gale Crater, Mars

The Sample Analysis at Mars-Evolved Gas Analyzer (SAM-EGA) on the Curiosity rover detected hydrogen chloride (HCl) and sulfur dioxide (SO2) gas evolutions above 600 °C and 700 °C, respectively, from several drilled rock and soil samples collected in Gale crater, which have been attributed to NaCl and Mg sulfates. Although NaCl and Mg sulfates do not evolve HCl or SO2 within the SAM temperature range (<~870 °C) when analyzed individually, they may evolve these gases at <870 °C and become detectable by SAM-EGA when mixed. This work aims to determine how Mg sulfate and NaCl interact during heating and how that affects evolved HCl and SO2 detection temperatures in SAM-EGA. Solid mixtures of NaCl and kieserite were analyzed using a thermogravimeter/differential scanning calorimeter furnace connected to a quadrupole mass spectrometer, configured to operate under similar conditions as SAM, and using X-ray diffraction of heated powders. NaCl analyzed individually did not evolve HCl; however, NaCl/kieserite mixtures evolved HCl releases with peaks above 600 °C. The results suggested that kieserite influenced HCl production from NaCl via two mechanisms: (1) kieserite depressed the melting point of NaCl, making it more reactive with evolved water; and (2) SO2 from kieserite decomposition reacted with NaCl and water (i.e., Hargreaves reaction). Additionally, NaCl catalyzed the thermal decomposition of kieserite, such that the evolved SO2 was within the SAM-EGA temperature range. The results demonstrated that SAM-EGA can detect chlorides and Mg sulfates when mixed due to interactions during heating. These phases can provide information on past climate and mineral formation conditions.

Industrial scale fouling of heat exchangers in isocyanate production

The fouling of a commercial stainless steel (AISI 316L) during the manufacture of polymeric methylene diphenyl diisocyanate (pMDI) has been studied using laboratory‐based fouling apparatus that simulates commercial production conditions. The goal of the work is to understand the mechanisms behind the corrosion and fouling during isocyanate production with a view to improving process efficiency, not only in this process, but also others using similar plant and processes. Steel coupons were exposed to a solution of pMDI and solid amine hydrochloride, with hydrogen chloride gas being bubbled through the reaction cell. A number of different conditions were investigated, the variables being pMDI concentration, HCl gas flow duration, immersion time and temperature. Following the fouling experiments the coupons were removed from the fouling rig, photographed, and examined by XPS and ToF‐SIMS; principal component analysis was used to extend the ToF‐SIMS analysis to identify organic fouling products. The extent of fouling is shown to be relatively insensitive to pMDI concentration, but significantly influenced by continual HCl flow and increased temperature, features which increase the extent of substrate corrosion thought to be a precursor to the fouling process itself. Both XPS and ToF‐SIMS confirm the formation of various nickel chlorides in the corrosion process. Urea and metal corrosion products are found to co‐exist on certain (random) areas of the coupon surface.

Weakening the integrity of waxy starch granules by selective degradation of amorphous matrices using gaseous hydrogen chloride

Waxy corn starch with 6–12 % moisture was degraded by gaseous hydrogen chloride (HCl(g)) then characterized chromatographically and microscopically to investigate the relationship between moisture-resulting changes in unit chain properties of starch and its susceptibility to swelling. Starches with the highest degradation extents at different moisture content had recoveries of 76–83 % (w/w) and the weight-average degrees of polymerization of 66–93 anhydroglucose unit. Additionally, the HCl(g)-degraded starches were still of birefringent granules but with internal cavity. When increasing the swelling temperature from 25 to 40 °C, some granules showed enlarged internal cavity, and some were fragmented. Change in granule morphology, accompanied by leaching of constituting polymers, was particularly evident for starch with preferential degradation of B1 chains over B2+ chains as the moisture content decreased from 9 % to 6 %. These findings not only manifest the impact of changes in B2+ and B1 chains on the swelling characteristic of HCl(g)-degraded granules, but also demonstrate an approach for weakening the integrity of granules by selective degradation of amorphous matrices using HCl(g).

Preparation and characterization of polyvinyl chloride based carbon materials with high specific surface area

Using PVC as raw material and KOH as activator, the carbon adsorption material with ultra-high specific surface area up to 5677.2 m2/g was prepared by chemical activation method, and its structure was characterized to study its adsorption performance on methylene blue solution; the activated mixture was analyzed for chlorine element and the recovery of chlorine element was calculated. The results show that the surface of the obtained activated carbon material is in the shape of smooth lotus root flakes with well-developed pore structure; the adsorption value of methylene blue adsorption can reach 765.0 mg/g, which can adsorb methylene blue solution quickly and efficiently; the elemental chlorine can be recovered efficiently with a recovery rate of 95.33 %, which can effectively reduce the toxic hydrogen chloride gas produced in the process of PVC pyrolysis. Excellent adsorption capacity of H2, CO2 and CH4. This experiment can provide an effective method for the harmless treatment of PVC.

Imine-Linked 2D Conjugated Porous Organic Polymer Films for Tunable Acid Vapor Sensing.

Two-dimensional (2D) films of conjugated porous organic polymers (C-POPs) can translate the rich in-plane functionalities of conjugated frameworks into diverse optical and electronic applications while addressing the processability issues of their crystalline analogs for adaptable device architectures. However, the lack of facile single-step synthetic routes to obtain large-area high-quality films of 2D-C-POPs has limited their application possibilities so far. Here, we report the synthesis of four mechanically robust imine-linked 2D-C-POP free-standing films using a single-step fast condensation route that is scalable and tunable. The rigid covalently bonded 2D structures of the C-POP films offer high stability for volatile gas sensing in harsh environments while simultaneously enhancing site accessibility for gas molecules due to mesoporosity by structural design. Structurally, all films were composed of exfoliable layers of 2D polymeric nanosheets (NSs) that displayed anisotropy from disordered stacking, evinced by out-of-plane birefringent properties. The tunable in-plane conjugation, different nitrogen centers, and porous structures allow the films to act as ultraresponsive colorimetric sensors for acid sensing via reversible imine bond protonation. All the films could detect hydrogen chloride (HCl) gas down to 0.05 ppm, far exceeding the Occupational Safety and Health Administration's permissible exposure limit of 5 ppm with fast response time and good recyclability. Computational insights elucidated the effect of conjugation and tertiary nitrogen in the structures on the sensitivity and response time of the films. Furthermore, we exploited the exfoliated large 2D NSs and anisotropic optoelectronic properties of the films to adapt them into micro-optical and triboelectric devices to demonstrate their real-time sensing capabilities.

Synthesis of methyl 3,4-anhydro-6-bromo-2-o-tert-butyldimethylsilyl-6-deoxy-α-d-allopyranoside from α-d-glucose

Some of simple carbohydrates and their derivatives are used clinically for the treatment of various diseases. Epoxide derivatives, which can be obtained by the intramolecular elimination of water from two vicinal hydroxyl groups, are stable, but sufficiently reactive compounds very often used as intermediaries in various syntheses. Synthesis of epoxide derivative, methyl 3,4-anhydro-6- bromo-2-O-tert-butyldimethylsilyl-6-deoxy-?-D-allopyranoside from ?-D-glucose was achieved in high yields in the minimal number of synthetic steps. Anhydrous glucose was used as a starting material which was transformed into methyl ?-D-glucopyranoside using dry, gaseous hydrogen chloride. Thus obtained derivative was treated with benzaldehyde in the presence of zinc chloride as Lewis acid giving methyl (R)-4,6-O-benzylidene-?-D-glucopyranoside. Obtained compound was treated with NBS (N-bromosuccinimide) in dichloromethane in the presence of barium carbonate giving methyl 4-O-benzoyl-6-bromo-6-deoxy-?-D-glucopyranoside. In the next step obtained compound was treated with TBDMSCl (tert-butyldimethylsilyl chloride) in pyridine, and methyl 4-O-benzoyl-6-bromo-2-O-tert-butyldimethylsilyl-6-deoxy-?-D-glucopyranoside was further mesylated, and obtained methyl 4-O-benzoyl-6-bromo-2-O-tert-butyldimethylsilyl-6-deoxy-3- O-mesyl-?-D-glucopyranoside was treated at the end with KOH to give methyl 3,4-anhydro-6-bromo-2-O-tert-butyldimethylsilyl-6-deoxy-?-D-allopyranoside (yield 78 %).

Production of Water-Soluble Carbohydrates from Aspen Wood Flour with Hydrogen Chloride Gas.

The aim of this study was to optimize the reaction conditions for concentrated acid hydrolysis of aspen wood flour by employing anhydrous hydrogen chloride gas to produce fermentable sugars. Gas hydrolysis with HCl was conducted both with and without temperature control during hydrolysis under a relatively low pressure of 0.1 MPa. Process parameters for HCl gas hydrolysis included the moisture content of aspen wood flour (0.7-50%) and reaction time under pressure (30 min to 24 h). In addition, liquid-phase hydrolysis with concentrated hydrochloric acid was conducted in concentrations of 32-42% and 15 min to 24 h reaction times for comparison with the gas-phase process. The highest yields (>90%) for water-soluble carbohydrates from aspen wood flour were achieved with temperature-controlled gas hydrolysis using 50% moisture content and 2 h total reaction time, which is in line with the previous research and comparable to hydrolysis with concentrated (42%) hydrochloric acid.

Synthesis of New 2-Substituted Fused Thienopyrimidin-4-ones by Bubbling Hydrogen Chloride Gas through an Alcoholic Solution of [b]-Fused 2-Amido-3-cyanothiophenes and Their Antibacterial Activity

Synthesis of New 2-Substituted Fused Thienopyrimidin-4-ones by Bubbling Hydrogen Chloride Gas through an Alcoholic Solution of [b]-Fused 2-Amido-3-cyanothiophenes and Their Antibacterial Activity

Secondary defects of as-grown oxygen precipitates in nitrogen doped Czochralski single crystal silicon

In this work, as-grown defects and their secondary defects in 300 mm nitrogen-doped Czochralski-grown single-crystal silicon (NCZ-Si) are investigated. Secondary defects are revealed by homogeneous epitaxial layer growth, and as-grown defects are decorated via gaseous hydrogen chloride (HCl) etching. Localized light scattering (LLS) technique is utilized to inspect defect distribution and provide the latex sphere equivalent (LSE) size to differentiate defect types. With the locations of LLS, the morphology of defect is observed by scanning electron microscopy (SEM). According to the results, it indicated that secondary defects are extrinsic dislocation loops and stacking fault (SF) loops, which are induced by as-grown oxygen precipitates during the growth and cooling process. Furthermore, the correlation between the counts of secondary defects and nitrogen concentration is obtained. It contributes to the optimization of nitrogen doping to avoid the generation of detrimental defects for device operation.

A novel plumes treater for solid rocket motors during hot‐firing tests using ice tunnel structure

AbstractAiming at the perniciousness of the exhausted plumes from solid rocket motors during hot‐firing tests, a novel plume treater is proposed using the ice tunnel device. The feasibility and effectiveness of this ice tunnel treater were successfully verified by tests on two solid rocket motors, XX 127 and XX 500, with different fuel charges of about 1.5 and 700 kg, respectively. Results show that the plume temperature could be greatly reduced from around 2000 to below 100°C through the ice tunnel for both motors, and the effect of noise reduction as well as the elimination of gaseous hydrogen chloride was also measured to be available in the test of XX 500, indicating the new ice tunnel treater could quickly achieve the “three reductions” of high temperature, serious noise, and gas pollution of the solid rocket motor emissions. Besides, a numerical model considering the factors of air entrainment, afterburning, convective heat transfer, radiation heat transfer, and phase change was established to investigate the flow and heat transfer behaviors within the ice tunnel. The plume temperature at the outlet of the ice tunnel was in good agreement with the experimental data. The intensity of afterburning is mainly determined by the amount of entrained air and the CO concentration. The cooling capacity of the ice tunnel is mainly contributed by convection, air entrainment, and particle radiation. This work could provide new ideas and references for the technological upgrade of the ground test platforms for solid rocket motors.

CORROSION BEHAVIOR OF SS304 IN HYDROGEN CHLORIDECONTAINING ENVIRONMENTS

The corrosion behaviour of stainless steel SS304 was investigated in three major aqueous environments, namely dry, water-saturated and free-water conditions and in two different methanol environments, namely dry and watersaturated environments with 99% methanol +1% water. The sulfuric acid and sodium chloride reaction generated hydrogen chloride gas in all the experiments. An inert carrier gas such as argon pushed the hydrogen chloride gas to flow over desiccants to make the latter dry. The dry hydrogen chloride gas would then flow into the second flask to which a pre-weighted stainless-steel specimen was exposed at ambient conditions for 48 hours. The specimen was retrieved and subjected to the surface and chemical analysis using Scanning Electron Microscopy (SEM)/EDAX. The presence of chloride would affirm the adsorption of chloride ions on the metal surface and vice versa. The specimen was then weighted to determine the corrosion rate. The results suggested that stainless steel would not corrode in dry hydrogen chloride gas. However, when saturated with moisture, its corrosion rate would increase by about one order of magnitude. In a free-water environment, the corrosion rate would triple. Hydrogen chloride gas would react with moisture or water, turning it into hydrochloric acid. Hydrochloric acid is a reducing acid that attacks the Cr2O3 layer, leading to general and/or localised corrosion. The presence of methanol increased the corrosion rate of stainless steel by a factor of three to four.Keywords: methanol, stainless steel, localised corrosion, methyl chloride

Study on leaching behavior differences of rare earth elements from coal fly ash during microwave-assisted HCl leaching

ABSTRACT Coal fly ash (CFA) as a potential resource for rare earth elements and yttrium (REY) has attracted extensive attention over the past few years. This paper focuses on studying microwave systems for the leaching of REY from CFA. Leaching parameters including hydrochloric acid (HCl) concentration, microwave heating time, microwave heating rate, and temperature were assessed. The optimal recovery of 74.91% REY, 86.77% light rare earth elements (LREY), and 34.79% heavy rare earth elements (HREY) are obtained at the conditions of 3 M HCl, T = 220°C, heating rate 39°C/min, and leaching time 30 min. The closed microwave system produces hydrogen chloride fluid or hydrogen chloride gas that is easier to react with CFA than hydrogen ions. It was revealed by the analysis of XRD, particle size, porosity, and SEM that fracture development benefits the entrance of leaching reagents into the inner layer of CFA. A positive linear correlation was found between leaching efficiency and REY3+ ionic radius. The stability of the REY-O bond also remains consistent with the ionic radius, leading to behavior differences during the leaching. This work was targeted to provide a theoretical and technological foundation for microwave-assisted HCl leaching for the extraction of REY in CFA.

Detection of HCl molecules by resonantly enhanced sum-frequency mixing of mid- and near-infrared laser pulses

We perform experimental studies of resonantly enhanced sum-frequency mixing (SFM), driven by tunable, spectrally narrowband mid-infrared and fixed-frequency nanosecond laser pulses, aiming at applications in molecular gas detection. The mid-infrared pulses are tuned in the vicinity of two-photon rovibrational transitions in the electronic ground state to provide strong resonance enhancements of the nonlinear susceptibility, while a probe laser at shorter wavelength uses an off-resonant single-photon coupling to excited electronic states. This SFM approach benefits from the advantageous combination of typically small detunings among the mid-infrared, vibrational transitions and the typically large transition dipole moment for couplings of electronic states. Moreover, compared to resonantly enhanced third harmonic generation (THG), a signal wave at much shorter wavelength permits simple and efficient detection. We demonstrate resonantly enhanced SFM via rovibrational states in gaseous hydrogen chloride molecules and compare its features to THG. The SFM spectra offer a large signal-to-noise ratio of 4 orders of magnitude and a detection limit down to a pressure of 0.1 mbar, corresponding to a particle density of $0.35\ifmmode\times\else\texttimes\fi{}{10}^{15}$ per ${\mathrm{cm}}^{3}$.

Perovskite Nanowire Laser for Hydrogen Chloride Gas Sensing.

Detection of hazardous volatile organic and inorganic species is a crucial task for addressing human safety in the chemical industry. Among these species, there are hydrogen halides (HX, X = Cl, Br, I) vastly exploited in numerous technological processes. Therefore, the development of a cost-effective, highly sensitive detector selective to any HX gas is of particular interest. Herein, we demonstrate the optical detection of hydrogen chloride gas with solution-processed halide perovskite nanowire lasers grown on a nanostructured alumina substrate. An anion exchange reaction between a CsPbBr3 nanowire and vaporized HCl molecules results in the formation of a structure consisting of a bromide core and thin mixed-halide CsPb(Cl,Br)3 shell. The shell has a lower refractive index than the core does. Therefore, the formation and further expansion of the shell reduce the field confinement for experimentally observed laser modes and provokes an increase in their frequency. This phenomenon is confirmed by the coherency of the data derived from XPS spectroscopy, EDX analysis, in situ XRD experiments, HRTEM images, and fluorescent microspectroscopy, as well as numerical modeling for Cl- ion diffusion and the shell-thickness-dependent spectral position of eigenmodes in a core-shell perovskite nanowire. The revealed optical response allows the detection of HCl molecules in the 5-500 ppm range. The observed spectral tunability of the perovskite nanowire lasers can be employed not only for sensing but also for their precise spectral tuning.

Boron-carbon-silicon film chemical vapor deposition by boron trichloride, dichlorosilane and monomethylsilane gases

A boron-carbon-silicon film was formed by an atmospheric pressure chemical vapor deposition method using a gas mixture of boron trichloride, dichlorosilane and monomethylsilane in ambient hydrogen at 800–1000 °C. The boron, carbon and silicon concentrations in the obtained film were about 15–30 %, 0–10 % and 50–80 %, respectively. With the increasing monomethylsilane gas flow rate, the carbon and silicon concentrations in the obtained film increased and decreased, respectively. In the obtained film, various chemical bonds between the boron, carbon and silicon existed, except for the carboncarbon bond. The following conclusions were obtained. (i) The carbon atoms existing at the surface have a chemical bond with the boron atoms, but not with the carbon and silicon atoms. (ii) The surface intermediate compound of boron chloride helps incorporating the carbon, while that of dichlorosilane does not. (iii) The etching by the hydrogen chloride gas significantly influenced the film formation process at higher than 900 °C.